Conventional broadloom tufting machines designed for manufacturing carpet and artificial athletic turf in high volume are primarily characterized by having cooperating backing feed and tufting head assemblies. Typically, such backing feed assemblies are defined by an arrangement of feed and take-up rollers that convey an elongate sheet of backing fabric longitudinally through a tufting zone area in which yarn is inserted into the steppedly advancing backing. Differential rotation between feed assembly rollers stationed at opposing ends of the tufting zone creates longitudinal tension in the backing.
The tufting head portion of the typical broadloom machine generally features one or more elongate bars of yarn-delivering needles which are disposed above the horizontally oriented backing and aligned transverse to the direction of its movement, as well as an equivalent number of yarn-catching loopers that are disposed below the backing. Needles along the needle bar(s) each receive yarn, delivered by any of a variety of suitable yarn feed mechanisms, from a designated spool situated within a yarn creel. So, as the backing sheet travels past the tufting head, needle bars are continually reciprocated downward so that the needles along them penetrate and insert yarn into the backing in unison. The loopers operate in synchronicity with the needles such that, as each needle momentarily protrudes the backing, a corresponding looper catches its yarn before the needle returns upward. This repeated interaction produces “loop pile” tufts of yarn along the backing. Additionally, knives can be used to sever just-formed loops and thereby render “cut pile” tufts.
Where uniformly patterned carpet or vast monochrome sections of athletic turf are to be produced in high volume, a broadloom tufting machine's needle can span the entire transverse width of the backing material. The incremental, longitudinal progression of the backing material that immediately follows each stroke of the needle bar causes the laterally-aligned needles to form every longitudinal running row of tufts intended to be created across the lateral length of the backing sheet. Thus, the tufting needles stationed along the needle bar remain at constant lateral positions, and there is no need for them to be transversely shifted when creating carpet or turf sections having uniform tuft placement and yarn color. On the other hand, tufting machines exhibiting constant axis needle bar movement are generally not suitable for producing multicolored articles of tufted material. So, the prior art has seen tufting machines improved to enable their needle bars to shift laterally, relative to the backing, in order that the particular type of yarn delivered by particular individual needles be selectively inserted into the backing at specific tuft locations in accordance with a preconceived pattern. For example, U.S. Pat. No. 4,829,917 to Morgante, et al. discloses the use of a computer-controlled hydraulic actuator for shifting a needle bar into different lateral positions in response to pre-selected stitch pattern information stored in the computer. As another example, U.S. Pat. No. 5,979,344 to Christman, Jr. discloses the use of computer-controlled inverse roller screw actuators for shifting needle bars laterally, as well as for shifting the backing sheet itself laterally, in order to tuft a graphic pattern of yarn into the backing as it advances longitudinally past transversely aligned needles.
Nevertheless, even with the lateral shiftability of their tufting heads, these prior tufting machines employing backing feed mechanisms are still not optimum for producing dynamic, multicolored tuft patterns like those often found in logo-bearing sections of athletic turf fields. The synchronous reciprocation of their bar-mounted needles is capable of producing only linear color patterns, and even lateral shifting of the needle bars can no more than produce diagonal or zigzagging patterns. Furthermore, since conventional tufting machines with backing feed mechanisms experience many subtle operational irregularities in the cooperative motions of their tufting head and backing feed components, the tuft patterns that they create tend to be somewhat imprecise. More specifically, tufting needles of prior art fed backing-type tufting machines reciprocate (along Z-axes) and may shift (along an X-axis) in timed relationship with the backing fabric's stepped longitudinal progression (along a Y-axis) past those needles, and whenever that three-axis motion relationship is altered in an unplanned way, the tufting needles fail to insert yarn tufts precisely at intended positions. For example, any sudden tag or surge in the feed mechanism's operation can create irregularity in the longitudinal spacing between successive tufts within rows, and any lateral skewing of the backing sheet can displace tuft rows entirely. The result of either occurrence may be noticeable distortion of the overall graphic image being created.
In addition, inherent characteristics of backing material itself tend to undermine the quality of the graphic output of these prior art machines. To wit, because backing sheets are typically fabricated of coarsely woven material, they are susceptible to being non-uniformly stretched in either direction as feed rollers advance them through a tufting zone. Since athletic field logos, for example, are almost always too large to be entirely formed within the lateral boundaries of a single machine's tufting zone—which is typically not more than feet wide—they must be created in pieces by individually tufting separate sheets of backing material and then gluing those sheets contiguously onto a base layer material. This leaves open the possibility that one image-bearing section of backing will progress through the tufting zone differently, in some respect, than does another section that will be adjacently laid section and will, thus, create visible color discontinuity within the installed composite image. Therefore, in the process of tufting separate graphically patterned artificial turf pieces for a single installation, it is important to ensure that tension applied to backing material remains consistent and that no unwanted lateral or irregular longitudinal movement of backing material occurs within the tufting zone.
Tufting head assemblies in which the tufting needles move two-directionally relative to a statically held backing sheet have been developed in the prior art to address these stability concerns related to production of dynamic tuft patterns. For example, U.S. Pat. No. 5,743,200 to Miller, et al. discloses a tufting machine that employs a gantry-like component which is movable along a Y-axis and which carries a tufting head that is movable along an X-axis. The Miller tufting head is disposed above the backing material, and it is mounted to the gantry via its attachment to a frame which is gearably connected to and movable along the gantry. The tufting head generally comprises a cylinder that is slidably secured to the frame, a piston that reciprocates within the cylinder, a needle that is secured to the bottom end of the cylinder and a blade that is positioned within the needle and is secured to the bottom of the piston. The blade projects from and retracts into the needle to assist the needle in protruding down through the backing to form loop pile tufts therein. The Miller tufting machine also includes a second, lower gantry that spans transversely below the backing material and moves along a Y-axis in synchronicity with the upper gantry. This lower gantry provides underlying support for the backing material in order to limit the downward deflection that would otherwise result from the pressure applied by the blade and needle operating on the backing.
Another example is found in U.S. Pat. No. 7,814,850 to the present inventor, John Bearden. That patent discloses a tufting machine with a dual-beam gantry configuration and that includes a computer-controlled tufting head adapted to move along X and Y axes in order to insert various yarns at precise locations along a clamped down and statically held backing in accordance with a design pattern which is stored in the computer. It also discloses a tufting head for producing precise graphic tuft patterns that is defined by having two distinct and asynchronously driven parts: (a) a needle carriage that is movably mounted along the upper gantry beam (i.e., above the backing) and features a number of separately operating tufting needles that are selectively reciprocated to insert tufts as the carriage journeys along an X-axis; and (b) a looper carriage that is movably mounted to the lower beam (i.e., below the backing) and is not mechanically connected to the needle carriage, but rather is selectively advanced to and fro along that beam in non-unison with the needle carriage such that a single looper and cutter pair may selectively cooperate with each one of multiple carriage needles as they individually downstroke.
Nevertheless, while tufting head mobility allows backing sheets to be stably fixed in place while being operated upon and, thus, allows the tensions applied to workpiece backing sheets to be repeatedly replicated, prior art fixed backing-type tufting machines tend to have lower production throughput than do their fed backing counterparts for a couple of specific reasons. First, with fixed backing-type machines, between successive iterations of clamped backings being manually swapped out by human operators, tufting is performed on individual backing pieces whose dimensions are limited to the generally rectangular dimensions of the machines' tufting zones. Because of those limitations, if a single fixed backing-type machine of the prior art is being used to tuft and entire athletic field, the required manual interludes add an amount of time to the tufting process that is directly proportionate to the ratio of the total size of the tufted field to the size of the machine's tufting zone. In other words, the greater the quantity of separate backing sheets that must be successively tufted due to dimensional limitations of the fixed backing machine's tufting zone, the more process-slowing manual intervention will necessarily be involved in the start-to-finish process of tufting the field.
In some instances, this dynamic has led to athletic turf manufacturers having to invest in multiple units of similar or identical tufting machines and the manufacturing facility space needed to accommodate all of them in order to meet production demands. In other instances, it has led to athletic field purchasers obtaining the multiple tufted backing sections that are to form a single field installation from separate vendors: one vendor which is better suited for high throughput production of vast, more monochromatic sections of the field (e.g., green areas) and another vendor which is better equipped to produce smaller, more color diverse image sections in higher quality. Moreover, aside from any manufacturing inefficiencies, the more discrete backing pieces that are to be part of a field installation, the more laborious the installation process becomes, as installers must meticulously lay the distinct pieces side-by-side atop a base surface, rather than being able to simply unroll a continuous sheet of backing that covers an equal-sized area. So, especially where graphic pattern tufting is involved, it is a constant production goal to minimize the quantity of distinct articles of tufted backing that are to comprise a single turf installation.
Accordingly, the present invention significantly contributes toward that goal by introducing a method for using a tufting machine in order to produce sections of graphically tufted turf under conditions of backing stability achieved by prior art fixed backing-type machines, but that, without manual intervention, allows for continuous tufting of a backing section of more than twice the length of that which could be by prior fixed backing-type machines of equivalent tufting zone length and occupying the same amount of floor space.